It is known that a non-pneumatic tire may be made by first forming a length of tire stock material and joining the ends together in such a manner as to provide a continuous tire, as described in U.S. Pat. No. 1,622,546, granted to G. W. Sieberling on Mar. 29, 1927, and in U.S. Pat. No. 4,033,395, granted to W. M. Berg et al. on July 5, 1977.
The Berg et al. patent describes a tire made from a continuous length of extruded thermoplastic material which is cut and adjoined at its ends to form a completed tire. Thermoplastic material has also been used to form cast non-pneumatic tires as taught by R. J. Wyman in U.S. Pat. No. 4,127,166, issued Nov. 28, 1978.
A serious deficiency of many non-pneumatic tires is in the hardness of ride provided by these tires. The Berg et al. patent attempts to overcome this deficiency by providing an inner chamber which is filled with a liquid urethane resin which reacts to form a solid tire. The Wyman patent, on the other hand, teaches that a softer ride may result if a non-pneumatic tire encloses an air chamber, such chamber being defined by the cross-sectional area of the cast tire and the cross-sectional area of the wheel rim to which the tire is attached, the tire being cemented in place to trap the air thus enclosed.
In both the Wyman and Berg et al. patents, however, the chamber so provided affords no structural integrity to the tire. Thus, in the Wyman patent, radial deforming forces applied to the tire cause pronounced collapse of the tire material into the chamber and the resiliency of ride offered by the material of the tire is compromised by the deformability of the tire body into the chamber. In the Berg et al. patent, the inner chamber is filled with urethane, which is substantially softer, and therefore less rigid, than the material of the outer tire.
What is desirable then, and is the object of the present invention, is to provide in a non-pneumatic tire means to impart structural integrity to the tire, but in such manner as the resiliency and ride of the tire may be controlled by appropriate changes in material of construction and configuration of the main tire body.
A further object of the present invention is to provide for the manufacture of such tire in a continuous extrusion process whereby costs of manufacture are minimized and process time is similarly minimized.
A further object of the present invention is to provide means for joining extruded tire stock material to form a completed tire in such a manner that the ends of the tire material are securely and irreversibly joined into a finished tire.